With increasing integration of integrated circuits, electronic devices such as power adapters and power supply apparatuses are developed toward minimization. As the volume of the electronic device is decreased, the problem associated with heat dissipation becomes more serious. Take a power adapter for example. The conventional power adapter comprises an upper housing and a lower housing, which are made of plastic materials and cooperatively defines a closed space for accommodating a printed circuit board. When the power adapter operates, the electronic components on the printed circuit board thereof may generate energy in the form of heat, which is readily accumulated within the closed space and usually difficult to dissipate away. If the power adapter fails to transfer enough heat to ambient air, the elevated operating temperature may result in damage of the electronic components, a breakdown of the whole power adapter or reduced power conversion efficiency.
Referring to FIG. 1, a schematic cross-sectional view of a conventional power adapter is illustrated. The power adapter 1 comprises an upper housing 11, a lower housing 12, a printed circuit board 13, a power input terminal (not shown) and a power output terminal 14. A closed space is defined between the upper housing 11 and the lower housing 12 for accommodating therein the printed circuit board 13. Many electronic components 131 are mounted on the printed circuit board 13. In order to remove most heat generated from the electronic components 131, several heat sinks 132 are usually provided on the printed circuit board 13. In addition, some electronic components 131 are coupled to the heat sinks 132 by screwing or riveting connection, thereby facilitating heat dissipation.
The heat dissipation mechanism of the power adapter 1 comprises conducting heat generated from the electronic components 131 to the heat sinks 132, radiating heat from the surfaces of the heat sinks 132 to the closed space of the power adapter 1, transferring heat from the closed space to the upper housing 11 and the lower housing 12 through air, and afterwards performing heat-exchange with the surrounding of the power adapter 1. Since the power adapter is developed toward minimization and designed to have higher power, the passive heat dissipation mechanism described above is not satisfactory.
For enhancing heat-dissipation efficiency, the heat generated from the internal electronic components of the power adapter 1 should be actively dissipated away the power adapter 1. In order to be applied to most operating statues and environments, the housing of the power adapter 1 should have additional openings such that the space defined by the housing is communicated with external ambient air. Under this circumstance, the power adapter 1 fails to be operated in humid surroundings or outdoors due to the poor waterproof properties. If the power adapter 1 having the active heat dissipation mechanism is used in the humid surroundings or outdoors, the electronic components may be damaged or shorted in case of contacting with water.
In views of the above-described disadvantages resulted from the prior art, the applicant keeps on carving unflaggingly to develop an electronic device with a waterproof and heat-dissipating structure according to the present invention through wholehearted experience and research.